Ownership can be transferred by the owner in the vehicle management window.
Server crossing: on '''Freedom servers''' you need to be owner of the boat to sail to another server(friends can cross as passengers provided the driver owns the boat), on '''Epic servers''' you can cross servers as friend too - the ownership transfers to the commander then.
The owner and any person with the ''Manage'' right can manage the usage permissions through a window available via the ''Manage vehicle'' menu option.